dt-bindings:iio:accel:domintech,dmard06: Move to trivial-devices.yaml

No need to maintain a separate document for such a simple binding.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201031182922.743153-8-jic23@kernel.org